1. Field of Invention
The present invention relates to the field of motor vehicle safety and relates more particularly to a hybrid gas generator used to inflate an airbag.
2. Description of Related Art
In recent years, new generators, called adaptive generators, have appeared so as to limit the risk of body accidents brought about by deployment of the airbag. To do this, various generators, coupled to suitable detection systems, allow the flow rate and/or the volume of gas to be modulated according to certain parameters, such as for example the morphology and the position of the passenger, the ambient temperature, and the nature and intensity of the impact. The generators are in all cases designed to operate fully within a time period of about fifty milliseconds.
Very recently, motor vehicle manufacturers have desired to incorporate devices using inflatable airbags to protect occupants when the vehicle rolls over. To do this, the airbags must remain inflated for a time period of the order of some 10 seconds. U.S. Pat. No. 5,967,550 discloses a generator provided with two pyrotechnic charges, the first serving to inflate the airbag within the milliseconds that follow the accident and the second allowing the airbag to remain inflated for some ten seconds. However, the geometry of this generator differs from the generators usually employed and therefore cannot be integrated into a vehicle in the places currently predefined by motor vehicle manufacturers. Patent application GB 2 316 475 discloses a generator fulfilling the same functions, using two separate gas reserves. However, this generator is relatively complex to produce since the two gas reserves are separated from each other by a plug which must be able, on the one hand, to guarantee sealing between the two reserves for a period of fifteen years and, on the other hand, to suitably fragment when the pressure starts to drop in the first gas reserve. Finally, patent application DE 20019665 discloses a generator provided with a pyrotechnic charge for rapidly inflating the airbag and with at least two separate fluids which act thereafter to keep the airbag inflated for several seconds.